1. Field of the Invention
The present invention relates to a light source of a non-self luminous display device, and more particularly to a liquid crystal display device having a backlight which includes a light guide plate and uses an LED as a light source.
2. Description of the Related Art
Recently, the liquid crystal display device has been popularly used as a display device. Particularly, the liquid crystal display device is used as a display part of portable equipment because the liquid crystal display device is thin and light-weighted, and consumes small electric power.
However, the liquid crystal display device is not a self-luminous-type display device and hence, the liquid crystal display device requires a lighting means. In general, as a lighting device which is used for the liquid crystal display device, a planar lighting device referred to as a backlight is popularly used. Although a cold cathode discharge tube has been used as a light emitting element (also referred to as a light source) of the backlight conventionally, an LED (light emitting diode) has been also recently used as the light emitting element.
The backlight includes a plate-shaped light guide plate. A material of the light guide plate is a light transmitting resin or the like, and light which is incident on the light guide plate from the light emitting element propagates in the inside of the light guide plate. A reflection/scattering member such as grooves, projections or a printed material is formed on the light guide plate, and the light which propagates in the inside of the light guide plate is directed and radiated toward a liquid-crystal-display-device side due to such a reflection/scattering member.
As a method of forming a light guide plate using a resin, there has been known a method which forms a light guide plate by filling a molten resin into a mold by injection molding. For example, JP-A-2005-103825 discloses a technique on a resin filling port for manufacturing a light guide plate by injection molding with high accuracy. However, JP-A-2005-103825 neither discloses nor suggests a manufacturing method of a light guide plate with respect to a case that the light guide plate has a small thickness.
Further, JP-A-08-313731 discloses a drawback on abnormal emission of light generated by a mark which is formed by an ejector pin for removing a light guide plate from a mold, and a shape of the ejector pin mark which can cope with the abnormal emission of light. However, JP-A-08-313731 neither discloses nor suggests the removal direction of the light guide plate and a shape of the light guide plate.